MTOA channel packed textures problem

[Shyralon]

Hello everyone!

I have a problem with using channel packed textures in Maya-Arnold.

Essentially I have three masks packed into the rgb channels of a texture.

When loading a single channel to extract a single mask, I get a weird result where darker parts of the other channels are still in the masks. Looks like a weird version of luminance or desaturated image. I would expect to get a clean mask as it is in Photoshop for example.

Left is the packed texture and the individual channels in Photoshop. Middle is my test shader and right is the result when extracting one of the masks. This happens with all my channel packed textures coming from quixel/substance, not only the test image.

Using Maya 2019 with the latest Mtoa (4.0.4.1 with Arnold Core 6.0.4.1) and ACES 1.0.3 as colorspace (not sure if that is relevant tho, also happens without aces)

Would really appreciate any help on this issue.

[lee_griggs]

Could you upload the texture map, please?

[Shyralon]

Yes, of course!

I attached the test texture and a simple project where the problem occurs.

Thanks for your help!arnold_rgb_test.zip

[Anonymous]

No problem if you extract the Red & Green channel with the Shuffle Node, you get a clean mask. The only problem is with the blue Channel

[Shyralon]

Just tried with the shuffle nide again, but could not manage to get a clean mask for any of the three channels by negating the remaining two channels 😕

[Anonymous · Accepted solution]

Work fine here Just put Specular Weight to zero

[lee_griggs]

Is your texture set to RAW?

[Stephen.Blair]

The test scene had Use Existing Tx turned off

[Shyralon]

That fixed it! I was using the shuffle node, but only clicked the "negate channel" for the other two channels. When I explicitly put the Green and Blue to "alpha" as you did I get a clean mask 🙂 Don't exactly understand why, but it works, so thanks a lot!

[Shyralon]

Thanks a lot for your replies! Both raw or utility-srgb-texture as well as use existing tx on and off gave the same results for me. But it is working with the answer below with using an aishuffle node.

[Stephen.Blair]

With Use Existing Tx turned off, it was the color management that was the problem.

With all the things I tried changing, I also changed the color space on the file node, but I forgot about that. That's why I didn't repro the problem (except just once)